PSN-L Email List Message

Subject: Re: Seismic intrusion detectors part 2
From: "Michael King" Mike@........................
Date: Thu, 10 Apr 2003 22:47:47 -0700


I would really like a way to reach this person.  thank you.
  ----- Original Message -----=20
  From: David H. Youden=20
  To: psn-l@.................
  Sent: Thursday, April 10, 2003 3:06 AM
  Subject: Re: Seismic intrusion detectors part 2


  Mr. King

  Are you aware that the National Institute of Science and Technology =
http://www.nist.gov has a mechanical engineering laboratory (MEL) which, =
in turn has a sensor laboratory studying exactly the subject of your =
question? The laboratory chief, E. Clayton Teague is a friend of mine, =
and I suggest that you get in touch with him. They are working with =
intrusion sensors that are smaller than a cigarette pack, have multiple =
sensors, and are networked via, I think 2.4 GHz radio. The idea is to =
spread a bunch of these along a trail and watch for intruders. If you =
need Clayton's e-mail address, and it's not on the website, please ask =
me.

  Dave...



  At 10:02 AM 4/9/03 -0700, you wrote:

    Here is the overall design.
    =20
    The sensor consists of (2) geophones.  They are places aprox. 30-40 =
feet apart on a known trail that illegals use.=20
    =20
    The prototypes we are using have (2) LT1677 opamp circuits that =
amplify the geophone outputs and feed the signal into a basic stamp 1.  =
The level of signal isn't converted to digital, the signal when large =
enough (about 1.67 volts) will drive the input pin high and thus we have =
a logic switch.
    =20
    In order to limit false hits the software in the basic stamp listens =
for a hit on a geophone.  When there is a hit it basically says if the =
second geopghone is hit within the next 2 seconds cancel the entire hit =
becuase it is most likely rain or some other seismic disturbance.  If =
the gephone is hit after that to seconds the it is a real hit and send a =
signal back to us through our repeater.  The data coming to us tells us =
what "port" hit first and what sensor it is.  By knowing what port was =
hit first we can tell what direction the contact is going. =20
    =20
    During initial powerup we callibrate the instrument by "walking the =
line" or walking by both geophones.  By doing this and counting the =
number of footfalls on an average man we can the have a rudimentary =
counting of the number of people walking by.  By dividing the number of =
detected footfall by the number of detected footfalls in the calibration =
we have the number of intruders.  It all works but the noisy circuit is =
killing me.
    =20
    This system works but our circuit is noisy and when I make the =
software just send hits on either geophone as they come in, sometimes, =
at random,  one or both of the "ports" will show hits for minutes on =
end.  If I touch the circuit board with my finger i can kill the noise =
until some kind of seismic activity start the noise again.
    =20
    =20
    =20
    =20
    Michael S. King
    Technical Director
    American Border Patrol







I would really like a way to reach this = person.  thank you.
----- Original Message -----
From:=20 David = H. Youden=20
To: psn-l@..............
Sent: Thursday, April 10, 2003 = 3:06=20 AM
Subject: Re: Seismic intrusion = detectors=20 part 2

Mr. King

Are you aware that the National = Institute of=20 Science and Technology http://www.nist.gov has a mechanical = engineering=20 laboratory (MEL) which, in turn has a sensor laboratory studying = exactly the=20 subject of your question? The laboratory chief, E. Clayton Teague is a = friend=20 of mine, and I suggest that you get in touch with him. They are = working with=20 intrusion sensors that are smaller than a cigarette pack, have = multiple=20 sensors, and are networked via, I think 2.4 GHz radio. The idea is to = spread a=20 bunch of these along a trail and watch for intruders. If you need = Clayton's=20 e-mail address, and it's not on the website, please ask=20 me.

Dave...



At 10:02 AM 4/9/03 -0700, you = wrote:
Here is=20 the overall design.
 
The sensor=20 consists of (2) geophones.  They are places aprox. 30-40 feet = apart on=20 a known trail that illegals use.
 
The prototypes we are using have (2) LT1677 opamp circuits = that=20 amplify the geophone outputs and feed the signal into a basic stamp = 1. =20 The level of signal isn't converted to digital, the signal when = large enough=20 (about 1.67 volts) will drive the input pin high and thus we have a = logic=20 switch.
 
In order to = limit false=20 hits the software in the basic stamp listens for a hit on a = geophone. =20 When there is a hit it basically says if the second geopghone is hit = within=20 the next 2 seconds cancel the entire hit becuase it is most likely = rain or=20 some other seismic disturbance.  If the gephone is hit after = that to=20 seconds the it is a real hit and send a signal back to us through = our=20 repeater.  The data coming to us tells us what "port" hit first = and=20 what sensor it is.  By knowing what port was hit first we can = tell what=20 direction the contact is going. 
 
During initial powerup we callibrate the instrument by = "walking the=20 line" or walking by both geophones.  By doing this and counting = the=20 number of footfalls on an average man we can the have a rudimentary = counting=20 of the number of people walking by.  By dividing the number of = detected=20 footfall by the number of detected footfalls in the calibration we = have the=20 number of intruders.  It all works but the noisy circuit is = killing=20 me.
 
This system = works but our=20 circuit is noisy and when I make the software just send hits on = either=20 geophone as they come in, sometimes, at random,  one or both of = the=20 "ports" will show hits for minutes on end.  If I touch the = circuit=20 board with my finger i can kill the noise until some kind of seismic = activity start the noise=20 again.
 
 
 
 
Michael S. King
Technical Director
American Border=20 Patrol

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